The present invention relates to film coatings for the coating of dosage forms of pharmaceutical or dietetic active ingredients or nutritional supplements, where the film coating compositions consist of a co-processed mixture of polyvinyl alcohol-polyether graft copolymer and polyvinyl alcohol (component A) and a vinylpyrrolidone-vinyl acetate copolymer (component B), organic or inorganic pigments (components C), optionally a surfactant, preferably a surfactant with an HLB value greater than 10 (component D) and further customary coating constituents. The film coatings are preferably intended to be used for instant-release coatings.
Solid administration forms are provided with a rapidly soluble coating for very different reasons. In this way, for example, it is possible to improve the appearance, the differentiability and the swallowability, to conceal a bitter taste or to protect the administration form against external influences such as e.g. moisture or oxygen. Since the film coating should dissolve rapidly in various aqueous media including in artificial gastric and intestinal juice, the most important constituent of the coating preparation has to be a water-soluble, film-forming polymer. For the coating of tablets, the film-forming polymers used are primarily hydroxypropylmethylcellulose and hydroxypropyl-cellulose, although these have serious disadvantages. For example, the viscosity of these polymers in water is very high and permits only a concentration up to ca. 10% since, on account of the high viscosity at relatively high concentrations, fine atomization in the spray nozzle is no longer possible and the coating becomes rough, inhomogeneous and unappealing. Furthermore, these polymers are very brittle and often suffer cracks during storage, particularly if the core alters its volume due to moisture absorption or release.
The use of polyvinyl alcohol-polyether graft copolymers as coating compositions or binders in pharmaceutical administration forms or as packaging material or as additive in cosmetic, dermatological or hygiene preparations is known, for example, from WO 00/18375. Thus, for example, a formulation for a film coating composition is described which consists of a polyvinyl alcohol-polyether graft copolymer and the customary coating constituents for coloring and covering, namely iron oxide, talc and titanium dioxide. Although a coating of this type is flexible, it is relatively soft and exhibits abrasion phenomena when shear forces act upon it. This plays a role particularly in the case of very large coating batches because then the high pressure caused by the large charge of the tablets in conjunction with the rolling movement of the tablets in the drum accordingly produces high shear forces. Since many medicaments and also some auxiliaries are very lipophilic, the coatings often do not adhere well to the tablet surface. Moreover, smoothness and shine of such film coating compositions are often unsatisfactory.
Polyvinyl alcohol is likewise known as film former, but is rarely used on account of various disadvantages. The use of polyvinyl alcohol-containing preparations which consist of polyvinyl alcohol, plasticizers and talc is described in WO 01/04195. Disadvantages of these preparations are the slow dissolution during the preparation of the aqueous coating solution, the high viscosity, the low concentration in the spraying solution, the use of plasticizers and the slow dissolution rate of the film coating, especially after storage, and also an embrittlement of the film coating following storage accompanied by cracking. Moreover, the spraying of relatively highly concentrated polyvinyl alcohol solutions (>8%) leads to thread formation at the spray nozzle.
The copolymers also referred to in the pharmacopoeia as copolyvidone or copovidone and obtained from N-vinylpyrrolidone and vinyl acetate in the weight ratio 60:40 is likewise known as film formers. Since the water absorption of copovidone is comparatively high, copovidone on its own is rarely suitable as film former and is usually combined with less hygroscopic substances in order to improve the brittleness and solubility of the film coatings. It is also mentioned that copovidone can be used as subcoating in order to protect tablet cores with moisture-sensitive active ingredients prior to the application of aqueous coating solutions or film coatings. (cf. V. Bühler, “Polyvinylpyrrolidone Excipients for Pharmaceuticals”, pp. 214-216, Springer Verlag Berlin Heidelberg 2005). However, copovidone on its own can only be applied as intermediate layer from an organic solution.
Pigments are an essential constituent of film coatings. In the film coating, they serve not only for coloring purposes, but can also develop a certain barrier effect. However, relatively high pigment contents in the film coating composition are disadvantageous from the point of view of application since, on the one hand, the incorporation of relatively high pigment fractions into an aqueous spray suspension is complicated, and, on the other hand, the spraying of suspensions with a high pigment content is also more difficult to control. Added to this is the fact that spray suspensions with a high pigment content have a greater tendency toward separation.
WO 03/070224 describes coatings which consist of polyvinyl alcohol-polyether graft copolymers, a component with hydroxy, amide or ester functions and further customary coating constituents. Here, firstly a premix of the feed substances is prepared as physical mixture and this is then dispersed in water. These preparations have a tendency toward separation and do not have good roughness values.
WO 2006/002808 describes rapidly dispersible film coating compositions based on polyvinyl alcohol-polyether graft polymers which, on account of particularly finely divided pigments, have a low roughness and good physical stability. Also described are combinations of two polymers such as, for example, a two-component combination of the graft polymer with a vinylpyrrolidone-vinyl acetate 6:4 copolymer. However, limits are imposed on such coating compositions for the pigment loading. The water-vapor permeation is also still not satisfactory in the case of such films.
In principle, film coatings with a high pigment loading of as far as possible 50% by weight or more are desired. However, film coating compositions with a relatively high pigment loading that are known hitherto do not meet the requirements for water-vapor permeation.